2010 Aveo, temp gauge will climb to H in steps, then after a moment will drop back down in steps. Car isn't physically running hot, heat works, fans work not losing fluod. Really weird thing is it will happen at the se points in my drive to/from work. I've done a vacuum assisted coolant replacement, and am positive there is no air in the lines. Good thermostat. Wondering if its the gauge or possibly the sensor.